These substances are known as constituents of hydraulic fluids according to German Patent 26 52 719. The hydraulic fluids described there have, in spite of their superior hydraulic properties, not yet been used on an industrial scale. The production route of the German patent by reaction of chloroalkylsilane esters with alcoholates has deficiencies and leads to incomplete reaction. Resin formation, low purity and high chlorine content, as a source of corrosion in the hydraulic system, prevent their use.